Radiopharmacist's Notes · Dose Calibrator QA Sources
Daily · monthly · annual —three QA bands, two owners.
A working dose-calibrator QA programme has three cadence bands and one handoff. The radiopharmacist runs daily constancy and monthly multi-isotope checks; the physicist runs the annual accuracy + linearity protocol. The same four-isotope reference set anchors all three. This post draws the bands and the handoff.
The three cadence bands
Tests, thresholds and what the log entry looks like
| Band | Trigger | Test | Pass | Fail | Log |
|---|---|---|---|---|---|
| Daily — radiopharmacist | Before first dose dispensed; after warm-up | Constancy reading on one long-lived reference (typical: Cs-137 or Co-57) | Δ within ± 5 % of decay-corrected expected activity | HOLD dispensing. Re-read after 5 min; if persistent, escalate to physicist | Signed constancy log entry; trend chart updated |
| Monthly — radiopharmacist | First working day of the month | Constancy reading on the full four-isotope set across the energy span | Δ within ± 5 % at every isotope; no consistent direction of drift across the month | Document and flag for the physicist annual-review file | Monthly QA log entry; cross-check against daily trending |
| Annual — physicist | Once per calendar year; before AERB inspection | Full accuracy + linearity protocol using the four-isotope set | Accuracy Δ within ± 10 %; linearity deviation ≤ 5 % across the clinical activity range | Quarantine dose calibrator until service / re-calibration; re-test before return-to-service | Annual QA dossier entry; result is one of the AERB inspection inputs |
Source: AAPM TG-181 PET / Nuclear Medicine QA; AERB Safety Code for Nuclear Medicine Facility (Section on dose-calibrator QA).
The handoff
Daily / monthly feeds annual
- The radiopharmacist owns daily and monthly. The physicist owns annual. The handoff is the monthly log + the trend chart — the physicist arrives for the annual already knowing the year-shaped drift pattern.
- The same reference set is used by both. The annual physicist accuracy / linearity reading is on the same sources the radiopharmacist reads every morning — the chain of evidence is unbroken from daily through annual.
- The physicist signs the annual dossier; the dossier goes into the AERB inspection file. The radiopharmacist signs the daily and monthly logs; those logs are the evidence the dossier rests on.
Replacement cycle
When each isotope in the set needs replacing
- Co-57 (T½ 272 d): replace annually, typically paired with the Co-57 flood-source replacement cycle. New source arrives ahead of old source's end-of-useful-life so the trending log spans the changeover.
- Cs-137, Ba-133, Co-60: multi-year service life. Replace when the source-to-background signal degrades below useful counting precision — typically every 5–10 years depending on initial activity and clinical activity range needed.
- Saxsons supplies the replacement source with calibration date aligned to the planned in-service date. The old source enters decay store and returns through the Source Return Service. AERB inventory updates on receipt of the disposal certificate.
Source: NNDC ENSDF half-life data; AAPM TG-181 source-replacement guidance.